SaratogaSkies Jim Solomon's Astropics


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Mercuryset over the Pacific

Mouse-over to see annotations. (Requires Javascript) Click to see high-res version.

Image Details:

Camera: Canon 5D
Mount: None
Scope: Canon EF 24-105 mm f/4L IS USM lens
Configuration: Prime Focus
Additional Optics: n/a (Prime)
Filter: None
Effective Focal Length: 82mm
Effective Focal Ratio: f/4
Exposure: 4 sec
Total Exposure: 0hrs, 0min
Date: 5/6/2008 8:59 PM PDT
Location: Russian Ridge Open Space Preserve
Acquisition: Manual
Focus: Auto
Dithering: None
Guiding: None


  • IRIS: RAW conversion, Dark subtraction, Bayer interpolation
  • JimP: Flat field, ASINH stretching
  • Photoshop: Shadows/Highlights, Levels, Resizing, JPG Conversion

Image Description:

This is a shot of the Moon, the planet Mercury, and the bright star Aldebaran (α Tauri) setting over the Pacific Ocean, captured with my friend Rob's Canon 5D and EF 24-105 mm f/4L IS USM lens. (Thanks Rob!) The Marine Layer can be seen covering the Pacific Ocean and the foreground coastal area. The camera is facing roughly in the direction of Half Moon Bay from where the tripod was set up. See also my image of the Sunset that preceded this shot by about 50min.

The Canon EF 24-105 mm f/4L IS USM zoom lens is nice and sharp, but it vignettes substantially at 82mm f/4 over the Canon 5D's full 35mm-sized chip. But any astrophotographer worth his salt will immediately think “Flat Fields!” in order to correct such things. And, sure enough, the image shown above has been corrected by Sky Flats. Mouse-over to see just how much vignetting was present before the Dark- and Flat-Fielding operations corrected it.

To capture this shot, I ventured up to the Russian Ridge Open Space Preserve, as it presented a perfect angle to the WNW and was sufficiently above the marine layer to prevent a fog-out. Of course, I had no business being there after sunset, and a not-very-amused Ranger kicked me out shortly after this image was taken. He did me a huge favor in so doing, however, as I was too brain-dead to remember to bring a flashlight with me and it was getting real dark at this time. Here's a map of the approximate place I set up my tripod to capture the shot:

View Larger Map

A higher resolution image is available. North is as indicated on the mouse-over.